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Understanding Periodicity: Covalent Radius, Ionisation Energy and Electronegativity in Chemistry
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Covalent Radius
The covalent radius is half the distance between the nuclei of two covalently bonded atoms. This measurement helps us understand atomic size trends.
Across a period, covalent radius decreases. This happens because as you move right across the periodic table, more protons are added to the nucleus while electrons go into the same shell. The stronger nuclear pull draws electrons closer to the nucleus, shrinking the atom.
Down a group, covalent radius increases. Each element down a group has an extra electron shell, making the atom physically larger. Inner electron shells also create a shielding effect that reduces the nuclear attraction on outer electrons.
Quick Tip: Remember the pattern - atoms get smaller as you move right across the periodic table, but larger as you move down a group.
First Ionisation Energy
First ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms. For example, with magnesium: Mg(g) โ Mgโบ(g) + eโป. This is always an endothermic process measured in kJ/mol.
Across a period, ionisation energy increases. The growing nuclear charge creates stronger attraction to electrons, making them harder to remove.
Ionisation Energy Trends
Down a group, ionisation energy decreases. Outer electrons are further from the nucleus and shielded by inner electron shells. This reduced attraction means less energy is needed to remove an electron.
The second ionisation energy involves removing another electron from an already positive ion. For example: Mgโบ(g) โ Mgยฒโบ(g) + eโป. This always requires more energy than the first ionisation energy because you're removing an electron from a positively charged ion where the remaining electrons are held more tightly.
To find the total energy needed to remove two electrons, you add the first and second ionisation energies together.
Remember: Second ionisation energies are always higher than first ionisation energies because you're removing an electron from a positively charged ion where electrons are less shielded and more strongly attracted to the nucleus.
Electronegativity
Electronegativity measures how strongly an atom attracts electrons in a chemical bond. This property helps predict bond polarity and molecular behaviour.
Across a period, electronegativity increases. As nuclear charge grows and atomic size shrinks, atoms develop a stronger pull on bonding electrons. This explains why non-metals (right side of the periodic table) typically form anions by gaining electrons.
Down a group, electronegativity decreases. Despite increasing nuclear charge, the greater number of electron shells creates a significant shielding effect. With bonding electrons kept further from the nucleus, the atom's electron-attracting ability weakens.
Exam Tip: Electronegativity trends follow the same pattern as ionisation energy - increasing across periods and decreasing down groups. This makes sense as both relate to an atom's ability to control electrons.
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This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
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I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
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Understanding Periodicity: Covalent Radius, Ionisation Energy and Electronegativity in Chemistry
Sophieeee ๐๐๐๐บ๐
@sophiesnotes
Periodicity is the study of trends in element properties across the periodic table. Understanding these patterns helps predict chemical behaviour and explains why elements react as they do. This summary explores key periodic trends including covalent radius, ionisation energy, and... Show more
Covalent Radius
The covalent radius is half the distance between the nuclei of two covalently bonded atoms. This measurement helps us understand atomic size trends.
Across a period, covalent radius decreases. This happens because as you move right across the periodic table, more protons are added to the nucleus while electrons go into the same shell. The stronger nuclear pull draws electrons closer to the nucleus, shrinking the atom.
Down a group, covalent radius increases. Each element down a group has an extra electron shell, making the atom physically larger. Inner electron shells also create a shielding effect that reduces the nuclear attraction on outer electrons.
Quick Tip: Remember the pattern - atoms get smaller as you move right across the periodic table, but larger as you move down a group.
First Ionisation Energy
First ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms. For example, with magnesium: Mg(g) โ Mgโบ(g) + eโป. This is always an endothermic process measured in kJ/mol.
Across a period, ionisation energy increases. The growing nuclear charge creates stronger attraction to electrons, making them harder to remove.
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Ionisation Energy Trends
Down a group, ionisation energy decreases. Outer electrons are further from the nucleus and shielded by inner electron shells. This reduced attraction means less energy is needed to remove an electron.
The second ionisation energy involves removing another electron from an already positive ion. For example: Mgโบ(g) โ Mgยฒโบ(g) + eโป. This always requires more energy than the first ionisation energy because you're removing an electron from a positively charged ion where the remaining electrons are held more tightly.
To find the total energy needed to remove two electrons, you add the first and second ionisation energies together.
Remember: Second ionisation energies are always higher than first ionisation energies because you're removing an electron from a positively charged ion where electrons are less shielded and more strongly attracted to the nucleus.
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Electronegativity
Electronegativity measures how strongly an atom attracts electrons in a chemical bond. This property helps predict bond polarity and molecular behaviour.
Across a period, electronegativity increases. As nuclear charge grows and atomic size shrinks, atoms develop a stronger pull on bonding electrons. This explains why non-metals (right side of the periodic table) typically form anions by gaining electrons.
Down a group, electronegativity decreases. Despite increasing nuclear charge, the greater number of electron shells creates a significant shielding effect. With bonding electrons kept further from the nucleus, the atom's electron-attracting ability weakens.
Exam Tip: Electronegativity trends follow the same pattern as ionisation energy - increasing across periods and decreasing down groups. This makes sense as both relate to an atom's ability to control electrons.
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This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
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Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
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Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because itโs too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH ๐๐๐ฒ๐ค๐โจ๐๐ฎ
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user